Deuteronomy 18:14-19:13
Those nations that you are about to dispossess do indeed resort to soothsayers and augurs; to you, however, the Lord your God has not assigned the like.
The Lord your God will raise up for you a prophet from among your own people, like myself; him you shall heed. This is just what you asked of the Lord your God at Horeb, on the day of the Assembly, saying, "Let me not hear the voice of the Lord my God any longer or see this wondrous fire any more, lest I die." Whereupon the Lord said to me, "They have done well in speaking thus. I will raise up a prophet for them from among their own people, like yourself: I will put My words in his mouth and he will speak to them all that I command him; and if anybody fails to heed the words he speaks in My name, I myself will call him to account. But any prophet who presumes to speak in My name an oracle that I did not command him to utter, or who speaks in the name of other gods--that prophet shall die." And should you ask yourselves, "How can we know that the oracle was not spoken by the Lord?" if the prophet speaks in the name of the Lord and the oracle does not come true, that oracle was not spoken by the Lord; the prophet has uttered it presumptuously: do not stand in dread of him.
When the Lord your God has cut down the nations whose land the Lord your God is assigning to you, and you have dispossessed them and settled in their towns and homes, you shall set aside three cities in the land that the Lord your God is giving you to possess. You shall survey the distances, and divide into three parts the territory of the country that the Lord your God has allotted to you, so that any manslayer may have a place to flee to. Now this is the case of the manslayer who may flee there and live: one who has killed another unwittingly, without having been his enemy in the past. For instance, a man goes with his neighbor into a grove to cut wood; as his hand swings the ax to cut down a tree, the ax-head flies off the handle and strikes the other so that he dies. That man shall flee to one of these cities and live. Otherwise, when the distance is great, the blood-avenger, pursuing the manslayer in hot anger, may overtake him and kill him; yet he did not incur the death penalty, since he had never been the other's enemy. That is why I command you: set aside three cities.
And when the Lord your God enlarges your territory, as He swore to your fathers, and gives you all the land that He promised to give your fathers if you faithfully observe all this Instruction that I enjoin upon you this day, to love the Lord your God and to walk in His ways at all times--then you shall add three more towns to those three. Thus blood of the innocent will not be shed, bringing bloodguilt upon you in the land that the Lord your God is allotting to you.
If, however, a person who is the enemy of another lies in wait for him and sets upon him and strikes him a fatal blow and then flees to one of these towns, the elders of his town shall have him brought back from there and shall hand him over to the blood-avenger to be put to death; you must show him no pity. Thus you will purge Israel of the blood of the innocent, and it will go well with you.